We mention here several other types of SE frontends [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}. The most successful strategy is multi-channel SE using a microphone array [1]}, [2]}, [3]}, [4]} which estimates beamformer (BF)-coefficients to minimize the ASR loss in an end-to-end manner. BF-based SE can enhance speech signals while introducing only a few distortions to the processed signals, which might be a reason for the success of this strategy. The proposed method is also inspired by this strategy in that it tries to avoid noise reduction that may cause distortion in speech and degrade ASR performance.
